1,720,973 research outputs found
Type Theory Unchained: Extending Agda with User-Defined Rewrite Rules
Full text linkDependently typed languages such as Coq and Agda can statically guarantee the correctness of our proofs and programs. To provide this guarantee, they restrict users to certain schemes a- such as strictly positive datatypes, complete case analysis, and well-founded induction a- that are known to be safe. However, these restrictions can be too strict, making programs and proofs harder to write than necessary. On a higher level, they also prevent us from imagining the different ways the language could be extended. In this paper I show how to extend a dependently typed language with user-defined higher-order non-linear rewrite rules. Rewrite rules are a form of equality reflection that is applied automatically by the typechecker. I have implemented rewrite rules as an extension to Agda, and I give six examples how to use them both to make proofs easier and to experiment with extensions of type theory. I also show how to make rewrite rules interact well with other features of Agda such as-equality, implicit arguments, data and record types, irrelevance, and universe level polymorphism. Thus rewrite rules break the chains on computation and put its power back into the hands of its rightful owner: Yours.Programming Language
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Afhankelijke patroonherkenning en bewijs-relevante unificatie
No full textDependent type theory is a powerful language for writing functional programs
with very precise types. It is used to write not only programs but also
mathematical proofs that these programs satisfy certain properties. Because of
this, languages based on dependent types – such as Coq, Agda, and Idris – are
used both as programming languages and as interactive proof assistants.
While dependent types give strong guarantees about your programs and proofs,
they also impose equally strong requirements on them. This often makes it
harder to write programs in a dependently typed language compared to one with
a simpler type system. For this reason certain techniques have been developed,
such as dependent pattern matching and specialization by unification. These
techniques provide an intuitive way to write programs and proofs in dependently
typed languages.
Previously, dependent pattern matching had only been shown to work in
a limited setting. In particular, it relied on the K axiom – also known as
the uniqueness of identity proofs – to remove equations of the form x = x.
This axiom is inadmissible in many type theories, particularly in the new and
promising branch known as homotopy type theory (HoTT). As a result, programs
and proofs in these new theories cannot make use of dependent pattern matching
and are as a result much harder to write, modify, and understand. Additionally,
the interaction of dependent pattern matching with small but practical features
such as eta-equality for record types and postponing of unification constraints
was poorly understood, resulting in subtle bugs and inconsistencies.
In this thesis, we develop dependent pattern matching and unification in a
general setting that does not require the K axiom, both from a theoretical
perspective and a practical one. In particular, we present a proof-relevant
unification algorithm, where each unification rule produces evidence of its
correctness. This evidence guarantees that all unification rules are correct by
construction, and also gives a computational characterization to each unification
rule.
To ensure that these techniques are sound and will stay so in face of future
extensions to type theory, we show how to translate them to more basic primitive
constructs, i.e. the standard datatype eliminators. During this translation, we
pay special attention to the computational content of all constructions involved.
This guarantees that the intuitions from regular pattern matching carry over to
a dependently typed setting.
Based on our work, we implemented a complete overhaul of the algorithm
for checking definitions by dependent pattern matching in Agda. Our new
implementation fixes a substantial number of issues in the old implementation,
and is at the same time less restrictive than the old ad-hoc restrictions. Thus it
puts the whole system back on a strong foundation. In addition, our work has
already been used as the basis for other implementations of dependent pattern
matching, such as the Equations package for Coq and the Lean theorem prover.
The work in this thesis eliminates all implicit assumptions introduced to the
type theory by pattern matching and unification. In the future, we may also
want to integrate new principles with pattern matching, for example the higher
inductive types introduced by HoTT. The framework presented in this thesis
also provides a solid basis for such extensions to be built on.status: Publishe
A sound unification algorithm based on telescope equivalences
No full textDependent pattern matching is arguably one of the best features of Agda. At the core of the algorithm for checking definitions by pattern matching lies a (first-order) unification algorithm. However, the implementation of this unification algorithm in Agda 2.4.* and earlier contains many additions that aren’t considered in the literature on dependent pattern matching, such as postponing of equations and support for eta-equality of record types. This mismatch between theory and implementation has caused numerous bugs, see #292, #473, #635, #1071, #1406, #1408, #1411, #1427, #1435, #1497 and #1613. In this talk, I will present a new way to think about unification by representing unification problems as telescopic equations, and unification rules as equivalences between these telescopes. This representation lies directly at the base of the new implementation of the unification algorithm in Agda 2.5.1.status: Publishe
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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